Paul Walker Crash -- Cops Investigating Possible Street Race

Cops are investigating the possibility that Paul Walker was in the middle of a high-speed street race with another car at the time he crashed and died this weekend ... TMZ has learned.

Law enforcement sources tell us ... investigators have received tips that Walker and the man driving the Porsche, Roger Rodas, had been racing prior to the crash ... and the high speed may have contributed to the wreck that killed both men.

Sources say ... the area where the crash occurred has a history of being a popular street racing location.

We're told cops are on the hunt for video and witnesses that could prove another car was involved.